To evaluate the SU-8 profile (i.e., how bad the "undercutting" is),
I simply cast some PDMS against it, cure, peel the PDMS off and
cut out a cross-section (thickness is not critical). Any bright-field
microscope (or even a simple stereoscope) can then help evaluate
the original feature profile.

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Nikola Pekas, graduate assistant
Department of Chemistry, Iowa State University